JPS6159555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite semiconductor device in which a semiconductor laser is combined with other optical functional elements. Semiconductor lasers have advantages such as small size, light weight, and high efficiency, and are therefore considered to be a powerful light source for optical communication devices and optical information processing devices. In order to apply laser light for various purposes, light modulation technology and light deflection technology to control the spatial position and direction of the light beam are required. Fortunately, semiconductor lasers can easily perform optical modulation by modulating the operating current. On the other hand, for optical deflection, it was necessary to use a separately prepared optical deflector. In addition to methods using mechanical rotation and displacement, methods using physical effects such as electro-optic effects and acousto-optic effects have been specifically proposed for optical deflectors.
used for each purpose. However, since these devices are provided with an external optical deflector, they have drawbacks such as an increase in the size of the device and a large coupling loss between the semiconductor laser and the optical deflector. The present invention provides a composite semiconductor device that improves the above-mentioned drawbacks by incorporating a light deflection function into a semiconductor laser. That is, a semiconductor laser with a double heterostructure with striped electrodes has a non-exciting region in the horizontal lateral direction without an optical waveguide mechanism inside the laser resonator, and a part of the non-exciting region has multiple polarization devices. The composite semiconductor device is provided with electrodes and has a structure in which at least one polarity electrode of the deflection electrode is electrically isolated from the excitation electrode of the semiconductor laser. According to the present invention, in a semiconductor laser, if a portion with large absorption loss is formed in the cavity mode in a part of the non-excited region that does not have a horizontal lateral optical waveguide mechanism inside the laser cavity, absorption The laser oscillates in a different transverse mode by avoiding areas with large losses, and when an electrode is provided in the non-excited region and current is injected into this electrode, the laser oscillates only in the mode that passes through this electrode. , it becomes possible to provide a semiconductor laser with an optical deflection function. The present invention will be explained below based on examples. Although the present invention can be applied regardless of the material of the semiconductor,
At present, GaAs is an excellent material.
A detailed explanation will be given with reference to the drawings, taking as an example a semiconductor laser having a double heterostructure consisting of AlxGa ₁ -xAs and having stripe electrodes. FIG. 1 is a schematic perspective view showing one embodiment of the present invention.
n-AlxGa ₁ -xAs layer 12 on GaAs substrate 11,
n-GaAs active layer 13, p-AlxGa ₁ -xAs layer 1
4.N-GaAs layers 15 are sequentially grown in multiple layers.
Here, 0.3 is usually used as x. The excitation region is a striped portion indicated by 16, which exists within the n-GaAs active layer. The n-GaAs active layer 1 is passed through the n-GaAs layer 15 only in this stripe portion.
P-type impurities such as Zn are selectively diffused to reach 3. (Not shown. The part of this p-type impurity diffusion region other than the n-GaAs active layer is a stripe electrode.) The p-side electrode metal 17 is applied to the entire surface of the side where the excitation region exists to improve heat dissipation. ing. In other words, the stripe portion 1 where p-type impurities are diffused
It has a so-called Brenna stripe structure in which only 6 is injected with current. A plurality of electrically isolated small p-side electrodes 19 for deflection are formed in a part of the non-excitation region 18 inside the resonator, and in the part of the deflection electrode 19 , like the stripe part 16, - P-type impurities such as Zn are selectively diffused through the GaAs layer 15 to reach the n-GaAs active layer 13 (not shown). An n-side electrode 20 is formed entirely on the lower surface of the n-GaAs substrate 11.
It also serves as the other polarity electrode (in this case, the n-side electrode) of the deflection electrode. In the above structure, first the stripe electrode and the n-side electrode 2
When a forward current is applied between 0 and 0, laser oscillation occurs when the current exceeds a certain threshold current _I1 . Since Zn is diffused in the deflection electrode 19 portion in the non-excited region so as to reach the n-GaAs active layer 13, the forbidden band width in that portion is equivalently narrowed by about 20 [meV]. Since there is no optical waveguide mechanism in the horizontal and lateral directions in the non-excitation region 18, laser oscillation occurs by selecting the optical path with the least loss in the resonator. Therefore, since the absorption loss at the laser oscillation wavelength is large in the deflection electrode 19 portion, the transverse mode of laser oscillation becomes a mode that avoids the deflection electrode 19 portion. Next, when a forward current is applied to one of the deflection electrodes 19 , transverse mode laser oscillation occurs through the energized portion of the one deflection electrode. At this time, the stripe portion 16
The threshold current I ₂ for laser oscillation that is energized is generally smaller than when the deflection electrode 19 is not energized (I ₁ ). However, when using one deflection electrode 19 that is distant from the stripe axis AB (see FIG. 2), I ₂ 〓I ₁ may occur. The mechanism for selecting the transverse mode of laser oscillation by the deflection electrode 19 will be explained as follows. In other words, it is thought that a so-called gain guiding mechanism exists in the plane direction of the excitation region of the stripe portion, while the non-excitation region 18 does not have this mechanism. Therefore, when the light that has been amplified to the excitation region enters the non-excitation region 18, the light spreads due to diffraction.
The laser resonator is composed of a pair of cleavage planes perpendicular to the stripe portion 16. Therefore, without the deflection electrode 19 , a mode passing along the stripe axis with the least diffraction loss will oscillate. However, if a portion having an absorption loss of a certain value or more is formed in a mode with least diffraction loss, oscillation occurs in a transverse mode in which the sum of diffraction loss and absorption loss is at least as small as possible. Deflection electrode 19
By injecting a current into the beam and giving gain to a portion of the diffracted light, it is possible to cause it to oscillate in a transverse mode in which the difference between diffraction loss and gain becomes smaller. It is well known that the diffraction loss increases as the mode deviates from the stripe axis. FIG. 2 schematically shows the plan view of FIG. 1 in order to explain the deflection angle obtained by the embodiment of the present invention, and the stripe axis is indicated by AB. Now consider the case where current is injected only into b of the deflection electrodes 19 . If the distance from the end of the stripe portion 16 to the deflection electrode 19 is taken and the interval between the deflection electrodes 19 is w, then the deflection angle θ within the crystal can be expressed as follows. θtan ^-1 (w/l) (1) Letting the refractive index of a semiconductor crystal be n, the deflection angle when the semiconductor crystal is exposed to air (n=1) can be expressed as follows. s ₁ ^-1 (nsin θ) (2) The deflection angle θ is not arbitrary; the threshold current for laser oscillation increases as θ increases, and when it exceeds a certain value θc, it becomes almost difficult to oscillate. θc is given by the following equation. θc4tan ⁻¹ (2λ/ns) (3) Here, s is the width of the stripe portion 16, and λ is the oscillation wavelength. If λ=8600 Å, n=36, and s=10 μm, θc11° and w/l0.19.
The deflection angle at this time is 43°. On the other hand, the spread angle of the laser beam within the junction plane can be approximately α4° at half width at half maximum, so if the resolution of this deflector is defined as p≡/α, p10 can be obtained. The composite semiconductor device of the present invention can be used, for example, to introduce a signal into any one fiber of a bundle of glass fibers arranged in a line within a bonding surface.
In addition, it can be used as a switching element or a deflection element for optical integrated circuits. As explained in detail above, by providing an unexcited region without a horizontal lateral optical waveguide mechanism in the laser resonator of a semiconductor laser and forming an electrode in this unexcited region, the semiconductor laser can be provided with an optical deflection function. be able to. In the detailed description of the present invention, GaAs
Although the case of a semiconductor laser made of -AlxGa ₁ -xAs has been described, it can be easily applied to a semiconductor laser made of other semiconductor materials, and a composite semiconductor device having similar effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an embodiment of the present invention, and FIG. 2 is a diagram for explaining the deflection angle obtained by the embodiment of the present invention. In the figure, 11 is an n-GaAs substrate, 12 is an n-
AlxGa ₁ -xAs layer, 13 is n-GaAs active layer, 14
is p-AlxGa ₁ -xAs layer, 15 is n-GaAs layer, 1
6 is a stripe part, 17 is a p-side electrode metal, 18
19 represents a non-excited region, 19 represents a deflection electrode, and 20 represents an n-side electrode.

Claims (1)

[Claims] 1 A double heterostructure semiconductor laser with striped electrodes has a non-excited region without a horizontal lateral optical waveguide mechanism inside the laser cavity, and a plurality of deflection electrodes in a part of this non-excited region. death,
A composite semiconductor device having a structure in which at least one polarity electrode of the plurality of deflection electrodes is electrically isolated from an excitation electrode of a semiconductor laser.